1. Field
The following description relates to an LED driving circuit, such as, for example, an LED driving circuit that senses an error of a power transistor that boosts an LED array.
2. Description of Related Art
Liquid Crystal Displays (LCD) are widely used because they are thinner and lighter and require less driving voltage and power consumption than other display apparatuses. However, since LCDs are non-luminous elements that cannot illuminate themselves, they need additional backlight for supplying light to an LCD panel.
Cold Cathode Fluorescent Lamps (CCFLs) and Light Emitting Diodes (LEDs) are widely used as backlight sources for LCD apparatuses. CCFLs utilize mercury and, as such, create environmental concerns. In addition, CCFLs have slow response speed, have low color reproducibility, and are not adequate for the compact size of an LCD panel.
On the other hand, LEDs do not use pollutant material. As a result, LEDs are relatively environmentally friendly. Further, LEDs are capable of impulse driving, which may serve to increase response speeds. In addition, LEDs have excellent color reproducibility and are able to adjust the light volumes of red, green, and blue light emitting diodes, thereby enabling changes to the brightness, color, and temperature of the light emitted therefrom. Moreover, LEDs are adequate for the compact size of LCD panels. Accordingly, LEDs are widely used as backlight sources in LCD panels.
In a case where a plurality of LEDs are connected in series, such as, for example, in an LED array, in an LCD backlight where LEDs are used, there is needed a driving circuit providing constant current to the LEDs and a DC-DC converter to adjust power to the LEDs. As an example, the DC-DC converter has a power transistor. The DC-DC converter inputs pulse width modulation (PWM) signals provided to a gate of the power transistor. Further, the DC-DC converter performs boosting to drive the LEDs.
Meanwhile, there are cases where such a power transistor is depleted by an extended driving of LEDs, shock, or the like. As such, when the power transistor is depleted, it is unable to maintain a desired output voltage to drive the LEDs. Thus, the power transistor is unable to perform boosting to drive the LEDs. Further, there is not an ability in the related art to sense power transistor depletion in order provide some sort of warning or corrective measure. As a result, the ability to sense power transistor depletion is highly desired.